Recently, there are increasing demands for reduction of fuel consumption in vehicles, and improvement of materials of a vehicle tire, particularly, of a tire tread in contact with the ground surface is required. So far, development of a material having low rolling resistance, namely, a material having a low hysteresis loss property, has been demanded. Besides, in order to reduce the weight of a tire, it is necessary to reduce the thickness of a tread portion of the tire, and there is a demand for a material having high abrasion resistance. On the other hand, a material used for a tire tread is required, from the viewpoint of safety, to be excellent in wet skid resistance and to have practically sufficient fracture characteristics.
A material meeting such requirements is a material containing a rubber and a reinforcing filler such as carbon black or silica. If, for example, a material containing silica is used, balance between the low hysteresis loss property and the wet skid resistance can be improved. Besides, an attempt has been made to reduce a hysteresis loss by improving dispersibility of silica in a material through introduction of a functional group having affinity or reactivity with silica into a molecular end of a rubber having high mobility, and further by reducing the mobility of the molecular end of the rubber through a bond with a silica particle.
For example, Patent Literature 1 proposes a modified diene-based rubber obtained by reacting a modifier having a glycidylamino group with a polymer active end. Besides, Patent Literatures 2 to 4 propose a modified diene-based rubber obtained by reacting alkoxysilanes having an amino group with a polymer active end, and a composition of such a modified diene-based rubber and silica. Furthermore, Patent Literatures 5 and 6 propose a polymer functionalized through a reaction of a cyclic aza-sila cycle compound with a polymer active end. In addition, Patent Literature 7 proposes a diene-based rubber obtained through a coupling reaction between a polymer active end and a multi-functional silane compound.